From d9d7b5b4d0779e16e5ba3103982351180de7df0e Mon Sep 17 00:00:00 2001 From: Campbell Barton Date: Sun, 4 Dec 2016 15:05:50 +1100 Subject: Cleanup: simplify bitmap line drawing - Expand overly dense & confusing delta assignments. - Replace bit shift with multiply. Also link to 'clipped' version of this function which may be useful to add later. --- source/blender/blenlib/intern/bitmap_draw_2d.c | 43 ++++++++++++++------------ 1 file changed, 24 insertions(+), 19 deletions(-) (limited to 'source/blender') diff --git a/source/blender/blenlib/intern/bitmap_draw_2d.c b/source/blender/blenlib/intern/bitmap_draw_2d.c index afc54511d13..e77e8cf40d0 100644 --- a/source/blender/blenlib/intern/bitmap_draw_2d.c +++ b/source/blender/blenlib/intern/bitmap_draw_2d.c @@ -46,6 +46,8 @@ /** * Plot a line from \a p1 to \a p2 (inclusive). + * + * \note For clipped line drawing, see: http://stackoverflow.com/a/40902741/432509 */ void BLI_bitmap_draw_2d_line_v2v2i( const int p1[2], const int p2[2], @@ -57,33 +59,36 @@ void BLI_bitmap_draw_2d_line_v2v2i( int x2 = p2[0]; int y2 = p2[1]; - int ix; - int iy; - - /* if x1 == x2 or y1 == y2, then it does not matter what we set here */ - int delta_x = (x2 > x1 ? ((void)(ix = 1), x2 - x1) : ((void)(ix = -1), x1 - x2)) << 1; - int delta_y = (y2 > y1 ? ((void)(iy = 1), y2 - y1) : ((void)(iy = -1), y1 - y2)) << 1; - if (callback(x1, y1, userData) == 0) { return; } + /* if x1 == x2 or y1 == y2, then it does not matter what we set here */ + const int sign_x = (x2 > x1) ? 1 : -1; + const int sign_y = (y2 > y1) ? 1 : -1; + + const int delta_x = (sign_x == 1) ? (x2 - x1) : (x1 - x2); + const int delta_y = (sign_y == 1) ? (y2 - y1) : (y1 - y2); + + const int delta_x_step = delta_x * 2; + const int delta_y_step = delta_y * 2; + if (delta_x >= delta_y) { /* error may go below zero */ - int error = delta_y - (delta_x >> 1); + int error = delta_y_step - delta_x; while (x1 != x2) { if (error >= 0) { - if (error || (ix > 0)) { - y1 += iy; - error -= delta_x; + if (error || (sign_x == 1)) { + y1 += sign_y; + error -= delta_x_step; } /* else do nothing */ } /* else do nothing */ - x1 += ix; - error += delta_y; + x1 += sign_x; + error += delta_y_step; if (callback(x1, y1, userData) == 0) { return; @@ -92,20 +97,20 @@ void BLI_bitmap_draw_2d_line_v2v2i( } else { /* error may go below zero */ - int error = delta_x - (delta_y >> 1); + int error = delta_x_step - delta_y; while (y1 != y2) { if (error >= 0) { - if (error || (iy > 0)) { - x1 += ix; - error -= delta_y; + if (error || (sign_y == 1)) { + x1 += sign_x; + error -= delta_y_step; } /* else do nothing */ } /* else do nothing */ - y1 += iy; - error += delta_x; + y1 += sign_y; + error += delta_x_step; if (callback(x1, y1, userData) == 0) { return; -- cgit v1.2.3